For convenience of the reader, the references referred to in the text are listed numerically in parentheses. These numbers correspond to the numerical references listed in the appended bibliography. By these references, they are hereby expressly incorporated by reference herein.
The ability of certain factors produced in very low concentration in a variety of tissues to stimulate the growth and development of bone marrow progenitor cells into granulocytes and/or macrophages has been known for nearly 15 years. The presence of such factors in sera, urine samples, and tissue extracts from a number of species is demonstrable using an in vitro assay which measures the stimulation of colony formation by bone marrow cells plated in semisolid culture medium. There is no reliable known in vivo assay. Because these factors induce the formation of such colonies, the factors collectively have been called Colony Stimulating Factors (CSF).
More recently, it has been shown that there are at least four subclasses of human CSF proteins which can be defined according to the types of cells found in the resultant colonies. One subclass, CSF-1 results in colonies containing predominantly macrophages. Other subclasses produce colonies which contain both neutrophilic granulocytes and macrophages; which contain exclusively neutrophilic granulocytes; and which contain neutrophilic and eosinophilic granulocytes and macrophages.
There are murine factors analogous to the first three of the above human CSFs. In addition, a murine factor called IL-3 induces colonies from murine bone marrow cells which contain all these cell types plus megakaryocytes, erythrocytes, and mast cells, in various combinations. Human IL-3 is also known. These CSFs have been reviewed by Dexter (1), Vadas (2), Metcalf (3) and Clark (4).
The invention herein is concerned with the recombinant production of proteins which are members of the first of these subclasses, CSF-1. This subclass has been further characterized and delineated by specific radioimmunoassays and radioreceptor assays--e.g., antibodies raised against purified CSF-1 are able to suppress specifically CSF-1 activity, without affecting the biological activities of the other subclasses, and macrophage cell line J774 contains receptors which bind CSF-1 specifically. The assays are described in (5).
Purification methods for various CSF proteins have been published. Purification has been reported for a CSF protein from murine L929 cells to a specific activity of about 1.times.10.sup.8 units/mg, which also stimulated mainly macrophage production (6). Purification of mouse L-cell CSF-1 to apparent homogeneity using a rabbit antibody column has been done (7). The first 25 amino acids of the murine sequence have been reported (8).
Purification of the CSF-1 from human urine has been described (6), and a human urinary CSF-1 obtained at a specific activity of 5.times.10.sup.7 units/mg which produced only macrophage colonies (5). The relationship of glycosylation of the CSF-1 proteins prepared from cultured mouse L-cells and from human urine to their activities was also described (9). Human urinary CSF-1 has been isolated to a specific activity of 10.sup.8 U/mg (10), and to a specific activity of 0.7-2.3.times.10.sup.7 U/mg on a rabbit antibody column (11).
A CSF protein from cultured human pancreatic carcinoma (MIAPaCa) cells was prepared which resulted in the growth of murine granulocytic and macrophagic colonies. The resulting protein had a specific activity of approximately 7.times.10.sup.7 units/mg (12).
Partially purified preparations of various CSFs have also been reported from human and mouse lung-cell conditioned media (13, 14); from human t-lymphoblast cells (15, 16); and from human placental conditioned medium to apparent homogeneity and a specific activity of 7.times.10.sup.7 U/mg (17).
A significant difficulty in utilizing CSF proteins in general, and CSF-1 in particular, has been their unavailability in distinct and characterizable form in sufficient amounts to make their employment in therapeutic use practical or even possible. The present invention remedies these deficiencies by providing starting materials to obtain purified human and murine CSF-1 in useful amounts through recombinant techniques.
Human and murine GM-CSF, which is a CSF protein of a different subclass, has been purified and the cDNAs cloned. This protein was shown to be distinct from other CSFs, e.g., CSF-1 (18). This GM-CSF protein is further described in PCT No. WO87/02060, published Apr. 9, 1987, as being useful to treat cancer patients to regenerate leukocytes after traditional cancer treatment, and to reduce the likelihood of viral, bacterial, fungal, and parasitic infection, such as in acquired immune deficiency syndrome (AIDS).
Murine IL-3 has been cloned (19). Human and gibbon I1-3 have also been cloned (20, 21). See also (22, 23, 24, and 25).
The cloning of a cDNA encoding a 224 amino acid form of human CSF-1, specifically the clone designated herein-below as pcCSF-17, is also published ((26): hereinafter Kawasaki), and in PCT No. WO86/04607, published 14 Aug. 1986. Recovery of a clone encoding a "long form" of human CSF-1 of 522 amino acids has also been reported (27, 28).